Totally transparent combo bass amp?

[Wisebass]

Hi fretlessman71

...does such a thing exist?

They always existed! Even Van Gogh had one and painted it! (under the table! )

And how would we know?

Yes they are hard to find!

greetings

Wise(b)ass

 

[fretlessman71]

I see it! Right next to the Emperor's New Clothes!

 

[Wisebass]

I see it! Right next to the Emperor's New Clothes!

thx for finding them

I thought these were in Hans Chritian Andersen's wardrobe!

 

[Redbrangus]

I was going to make a joke about how a totally transparent cab would be a constant tripping hazard on stage, but that territory has already been mined sufficiently.

Transparent is a fairly subjective term and impossible to quantify, so you're already pretty far off into cork-sniffing territory. Audiophiles use the term to describe a quality that is far beyond just flat frequency response. Frequency response is something that IS measurable, more or less, but I don't believe it's especially meaningful for a bass amp. The ultimate goal is the amplification of what is basically an electronic signal, not a hyper-pure reproduction of an acoustic event, like a violin playing in a recital hall. The sound of the instrument is the sound of the entire signal chain, most especially including the transducers at each end of the chain.

One of the goals of any sound reinforcement system is to have flat frequency response (within certain parameters), but I don't think one would describe the actual sound of them as 'transparent'. Neutral, perhaps (at their best), but hardly transparent in actual practice. IMHO, anyway.

 

[fretlessman71]

I guess the idea at the heart of my question is: how do you truly know what a given bass sounds like if it shall always be colored somewhat by the amp you play it through? And it seems like the answer is: you don't. It's always going to be a tone created by a combined effort of bass and amp at the very least. So what amps are CLOSER to flat than others, and how/why?

 

[agedhorse]

I guess the idea at the heart of my question is: how do you truly know what a given bass sounds like if it shall always be colored somewhat by the amp you play it through? And it seems like the answer is: you don't. It's always going to be a tone created by a combined effort of bass and amp at the very least. So what amps are CLOSER to flat than others, and how/why?

Let's look at it a different way...

Bass designers will use a variety of bass amps to tailor their instruments around what players will be using. That's why many builders have several amps that they will use to evaluate their instruments. They generally won;t worry about "flat response" because that's not how the vast majority will be used.

 

[pfschim]

View attachment 3851385

well,, to be fair, this is not "totally transparent" ... I can see the drivers and the amp is actually pretty opaque

 

[Foz]

It's not the CPU time, it's the window for the low frequencies.

At 4mSec, that's 1 full cycle at 250Hz or 1/10th of a cycle at 25Hz, which becomes estimation or interpretation territory.

My experience is that it's necessary to get at least 1/2 of a complete cycle and preferably a full cycle worth of sampling at the lowest frequency which corresponds to a gate time of ~20-40mSec, which means that the earliest boundary would need to be roughly 40 feet away...

Whaaaaa???

You use a chamber rated to 25 Hz?

I'd love to some pics and the spec. cert.s on that beast.

===

Also - wait a minute... If the nearest reflective boundary is 40' away then the distance traveled by a signal from the DUT to the first reflection and back to the DUT [or an adjacent measurement mic] = +/- 80' init?

and 1,130fps / 80' = 0.0708 seconds init?

 

[agedhorse]

Whaaaaa???

You use a chamber rated to 25 Hz?

I'd love to some pics and the spec. cert.s on that beast.

===

Also - wait a minute... If the nearest reflective boundary is 40' away then the distance traveled by a signal from the DUT to the first reflection and back to the DUT [or an adjacent measurement mic] = +/- 80' init?

and 1,130fps / 80' = 0.0708 seconds init?

Good points, I should have clarified...

The challenge that I was illustrating is that low frequency measurements in general are difficult to achieve accurately. I didn't mean to imply that 25Hz measurements were in fact done this way, but why they were difficult.

For the boundary example, I should have clarified that I was using a far field example like what would be used in live audio, where the measurement distance is generally at a distance greater than the first reflection (though complicated by the ground plane reflection, which is why I had mentioned it). IF the measurement was strictly near field, than an off axis boundary 40' (which could represent ~80mSec total path) away could generally be ignored as the level attenuation might be low enough to become insignificant.

Anechoic chambers for very accurate 25Hz measurements would be quite large, but smaller chambers with moderate wedge/baffle dimensions still have absorption at low frequencies. Maybe 50% absorption, maybe even 75% absorption, which is obviously better and more useful than the virtually 0% absorption of a typical boundary surface. When you get around 100Hz, things improve significantly and the errors decrease greatly.

I prefer outdoor measurements myself, and I have a suitable space to do these with boundaries very distant compared with the measurement distances.

The point I am making is that all methods of low frequency measurement are difficult, gating has challenges, anechoic chambers have challenges, small spaces have challenges, large spaces have (different) challenges, even outdoors has challenges.

 

[Wasnex]

I was going to make a joke about how a totally transparent cab would be a constant tripping hazard on stage, but that territory has already been mined sufficiently.

Transparent is a fairly subjective term and impossible to quantify, so you're already pretty far off into cork-sniffing territory. Audiophiles use the term to describe a quality that is far beyond just flat frequency response. Frequency response is something that IS measurable, more or less, but I don't believe it's especially meaningful for a bass amp. The ultimate goal is the amplification of what is basically an electronic signal, not a hyper-pure reproduction of an acoustic event, like a violin playing in a recital hall. The sound of the instrument is the sound of the entire signal chain, most especially including the transducers at each end of the chain.

One of the goals of any sound reinforcement system is to have flat frequency response (within certain parameters), but I don't think one would describe the actual sound of them as 'transparent'. Neutral, perhaps (at their best), but hardly transparent in actual practice. IMHO, anyway.

Yes transparent is a bit difficult to explain. To me the idea is the speaker allows the nuances of the source material to pass without being covered or concealed. Extended range and flat frequency response are definitely important factors. But even speakers with full range and flat frequency response will impose some of their own voicing and conceal some of the nuances of the sound source. Also the speaker with the flattest response will not necessarily be the most transparent.

In my experience HiFi speakers tend to be pretty flat and sound really sweet, but many tend to smooth out some of the mid range detail so they are not always as revealing and transparent as we want. In my experience musical instrument speakers often tend to be more revealing and articulate in mid range frequencies, but less detailed and accurate in the low end.

Masking is something else to consider. Masking occurs when one sound source covers up another, and it's a frequent problem in live music because you tend to only hear the dominant sound source. So if you want to hear a nuance of an instrument's tone that is encoded in a certain frequency range in a live setting, you may need to actually emphasize the frequency range so it jumps out a little. I.E. this is one reason flat response may not be ideal.

 

[Wasnex]

I guess the idea at the heart of my question is: how do you truly know what a given bass sounds like if it shall always be colored somewhat by the amp you play it through? And it seems like the answer is: you don't. It's always going to be a tone created by a combined effort of bass and amp at the very least. So what amps are CLOSER to flat than others, and how/why?

The user need to consider the bass, amp, and speaker as a system IMHO. You might want to throw the strings into the equation as well. Rather than choosing a flat amp, choose and amp you like. Of course if you like flat that fine.

 

[Liko]

...does such a thing exist? And how would we know?

We can know an amp is totally transparent by feeding it a specific known input, recording the output and subtracting the waveforms from each other. If you get absolute silence, the amp's transparent.

That sounds simple, but in practice what you get is the difference between two systems playing that input; the system you use to calibrate the measurement microphone, and the system under actual test. You can compensate for the color of your reference mic, but to know what that is you must feed it a test signal from a speaker that is known to be totally transparent.

That creates a chicken and egg situation, where you know the sum of harmonic distortion produced by both microphone and speakers in a loopback, M+S, and you can compensate for that, but what you really want is to compensate for is the mic's coloration M by itself. So, you try to subtract the speaker's distortion S. But how do you determine S? You have to measure it by performing the same loopback test with a different microphone with a known distortion. But that microphone's distortion is only known in the context of the speaker used to calibrate it, and that speaker's distortion can only be known in the context of another microphone. And on and on it goes.

At the end of the day, the very best you can do is a statistic amalgam produced by testing every combination of a series of mics and speakers against each other. You end up with the combined distortion pattern of one mic with every speaker and vice versa, and if you average them, hopefully the distortion of the speakers cancel out to nothing, and you end up with something imperceptibly close to the coloration of the microphone. You can then cancel that out of the measurement of the system under test.

Does it work? We hope so. But it's fundamentally flawed in that the closest you can get is the statistical error of the calibration of the microphone, and thus you can never be 100% sure an amplifier system is totally transparent, because you can never be 100% sure you're comparing it to a totally transparent reference.

 

[ClusterFlux]

I guess the idea at the heart of my question is: how do you truly know what a given bass sounds like if it shall always be colored somewhat by the amp you play it through? And it seems like the answer is: you don't.

Well....

There is an epistemological issue here, which is "what does a bass truly sound like on its own?" The problem is that there is no such condition. The instrument will always be played in an environment that, in some way shape or form, modifies the sound of the instrument. If you somehow had the Perfectly Transparent Amp in a small room with hardwood floors, it's going to sound slightly different than the same setup in a concert hall or an outdoor amphitheater.

In addition, the way you actually play the instrument will have a substantial impact on the sound. Strings, pickup location, pickup settings, passive vs active, pick vs slap vs fingers, various types of picking or slapping or finger techniques, preamps, EQ, any other effects... It all has an impact.

Also, the way we interpret the sound changes whether you are playing solo, or with an acoustic guitar, or a 3-piece, 4-piece, 5-piece or larger band. (That's in addition to the sound of the room and the amplification).

Another factor is expectations, which can play a huge role in our perceptions of various qualities. Merely telling someone "this recording is of a '59 Precision" when it's actually a cheapo no-name 80s P-bass copy could fool a lot of listeners. A very, very, very tiny percentage of people can make extremely fine distinctions, but it's lost on most people -- especially if that context is "bass frequencies mixed in with drums, guitars and keyboards by a bored sound engineer in a club where half the audience wants to get wasted." We have decades of research on this, even neurological studies (How expectation influences perception).

So, you could get close to an amplification system that confers as little coloration as possible -- again, a PA or studio reference equipment -- but you still won't ever really hear the bass "on its own."

To indulge in a bit of jargon: As a human being, you simply don't have access to these types of physical qualities "in itself" or noumenal sense. It will always be present as phenomena, as an experience mediated by the context of not just the instrumen'ts variations and amplification method and the room and the other instruments and how you play it, but by the very act of perception by the human brain/mind.

Of course, this is not unique to instruments. Any object of perception is subject to the same limitations. There is no such thing as a "pure" or "direct" perception of anything.

Despite all of this, we can, in fact, get an idea of the inherent characteristics of the equipment by hearing it in different contexts, and with different amplification techniques.

Thus, we turn back to your question....

So what amps are CLOSER to flat than others, and how/why?

Again, I think the real answer would be a PA or studio reference equipment.

But I think you're asking the wrong question. The goal is not to perfectly reproduce the inherent sound of the bass. It's to produce a pleasing sound that fits the context.

You personally may find that a flat response is pleasing, but I think you're in a very small minority... and for good reason. Bass guitars generally aren't intended to be amplified without coloration, thus they don't sound particularly good that way. Again, that's why there are so many preamp/DI pedals that color the tone.

 

[fretlessman71]

I should clarify: I'm not interested necessarily in purchasing such an amp (if one even existed). I was hoping to get a very heady interesting philosophical discussion going, and it seems that that's exactly what I have achieved with my posts. Thanks to all who have posted! Still reading and learning here.

 

[beans-on-toast]

Grace makes quality mic and instrument preamps. Their mic preamps for example, are used on symphony recordings where high fidelity is demanded.

Grace Design - High Fidelity Professional Audio Products

 

[seamonkey]

Lack of coloration, lack of measured deviation of the signal, is what I mean by transparency.
It it was glass, it would be clear transparent glass, no color, no frosting, no artifacts.

Sean Olive JBL Patent:
Method for predicting loudspeaker preference
"A method for predicting a loudspeaker preference rating that correlates the loudspeaker's preference rating, using a statistical regression model, to a measured deviation in a frequency response of a loudspeaker."

And Dr. Toole paper: “that flatness and smoothness of high resolution on-axis curves need to be given substantial weighting” in predicting loudspeaker preference." (Dr Toole is referenced in the above patent)

Both from double blind testing of trained listeners and regular listeners show evidence that flat frequency response, a low measured deviations, is what listeners prefer.

It's not audiophile foolery. Foolery is when people try to say it can't be objectively measured.

 

[agedhorse]

Lack of coloration, lack of measured deviation of the signal, is what I mean by transparency.
It it was glass, it would be clear transparent glass, no color, no frosting, no artifacts.

Sean Olive JBL Patent:
Method for predicting loudspeaker preference
"A method for predicting a loudspeaker preference rating that correlates the loudspeaker's preference rating, using a statistical regression model, to a measured deviation in a frequency response of a loudspeaker."

And Dr. Toole paper: “that flatness and smoothness of high resolution on-axis curves need to be given substantial weighting” in predicting loudspeaker preference." (Dr Toole is referenced in the above patent)

Both from double blind testing of trained listeners and regular listeners show evidence that flat frequency response, a low measured deviations, is what listeners prefer.

It's not audiophile foolery. Foolery is when people try to say it can't be objectively measured.

It may be preferred for the REPRODUCTION of music, but I can say with certainty that it's not preferred by those who are using a bass or guitar speaker for the CREATION of music. The linear and non-linear response of the amplifier and speaker greatly contribute to player's preferences.

In the reproduction of music, all of the tonal preferences have already been incorporated into the program material.

 

[Killed_by_Death]

Any amp with a Effects-Return, plug into that & you'll hear the instrument as transparent as it can get, except for whatever shading the speaker & cabinet give it.

 

[Wasnex]

We can know an amp is totally transparent by feeding it a specific known input, recording the output and subtracting the waveforms from each other. If you get absolute silence, the amp's transparent.

Lack of coloration, lack of measured deviation of the signal, is what I mean by transparency.

Unfortunately this sort of definition is not entirely useful for evaluating speakers because of the way they pretty much continually shift phase as the frequency changes. If you were to look at the phase response over the range of a typical speaker you would see many wraps of phase shift plot. AFAIK, Our ears are not particularly sensitive to phase distortion, so it doesn't have much of an impact on perceived transparency.

Image from this article http://www.hxaudiolab.com/uploads/2/5/5/3/25532092/a_meaningful_loudspeaker_phase_response.pdf

 

[lug]

Transparent amps have little to no mojo....there, I said it.